Electric muffle furnace



April 14, 1-925.

J. C. WOODSON ELECTRIC MUFFLE FURNACE Filed Oct. 2, 1922 haimha amw Fig. 2

WITNESSES:

INVENTOR Jizmes C. Waadson.

BY a

ATTORN EY Patented Apr. 14, 1925.

UNITED STATES PATENT OFFICE.

JAMES C. WOODSON, OF MANSFIELD, OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC v PRODUCTS COMPANY, A CORPORATION OF MICHIGAN.

ELECTRIC MUFELE FURNACE.

Application filed October 2, 1922. Serial No. 591,781.

To all whom it may concern:

Be it known that I, Jaanss C. iVooDsoN, a citizen of the United States, and a resident of Mansfield, in the county of Richland and State of Ohio, have invented a new and useful Improvementin Electric Muflie Furnaces, of which the following is a specification.

My invention relates to electric furnaces and, particularly, to electric-resistance fur-- naces of the muffle type.

The object of my invention is to provide a relatively simple, compact. rugged and inexpensive structure for relatively small portable. mufile furnaces.

In practicing my invention, I provide a tabular muffleof refractory material, upon which a suitable resistor member iswonnd and held in place thereon by an initially granular electrical-insulating material. I provide a suitable heat-insulating casing for the heating element and a suitable heatinsulating end disk at one thereof. I provide a suitable terminal member locate-d adjacent that end of the furnace at which the disk of heat-insulating material is located. A suitable metallic casing, having end caps to which suitable supporting members are secured, is provided. A Work-supporting member is provided adjacent the open end of the mufile, and the furnace is mounted on a suitable base.

In the single sheet of drawings,

Figure 1 is a view, in vertical longitudinal section, of a muffle furnace embodying my invention; and

Fig. 2 is a view, in vertical lateral sect-ion thereof, taken on the line IIII of Fig. 1.

An electric muflie furnace, designated generally b the numeral 11, comprises a tubular mu e 12 of a suitable electric-insulating and heat-conducting refractory material which is provided, on its outer surface, with a helical groove to receive a suitable resistor member 13, comprising a wire having a resistance to permit of being traversed by an electric current of suitable in tensity to produce the desired temperature within the muffle 12. A layer 14 of an electrical-insulating and initially granular material,such as alundum, is provided on the outer surface of the muffle 12 and covers the. resistor member 13 in order to prevent movement of the resistor member 13 relatively to the mufile. Upon heating up the furnace for the first time, the layer 14 bardens and serves to hold the resistor firmly in place.

A plurality of substantially semi-tubular heat-insulating members 15 surround the heating element, comprising the muflle 12, the resistor 13 and the layer 14, and are substantially co-extensivewith the length of the muflle. An end disk 16, of a refractory heat-insulating material, is located adjacent the one end of the muflie 12, the diameter of the disk 16 being substantially the same as the outer diameter of the two members 15. An end piece or closing member 17, of refractory material, is placed at that end of the mutl'le 12 which is operatively engaged by the disk 16 in order to provide an abutment for small articles placed within the muflie 12 to be heat-treated'therein or for tools which are inserted therein to be heated. A relatively thin disk 18 of heat-insulating material, such as mineral wool, is placed adjacent the outer surface of the disk 16.

A metallic casing and containing structure for the muillc and the surrounding heatinsulating members may comprise an openend thin metal tubular casing 19 having an end cap 21 secured thereto adjacent to the open end of the mutfie 12, which may be provided' with a central opening 22, slightly larger than the inner diameter of the mufile. A second end cap 23 is suitably secured to the other end of the open casing 19 and has a substantially central, circular opening 24. therethrough. A screw-threaded tubular collar 25 is secured to the cap 23 concentric with the opening 24;.

A terminal block 26, carrying terminal members 27 suitably secured thereto, is located within the collar 25 and is provided with an outwardly-extending tubular metal cover member 28 which is so formed as to have a larger diameter for that portion of its length which is in operative contact with the block 26 and a somewhat smaller diameter for that portion which extends outwardly from the block 26 and covers the terminal bars 27. A shoulder is thus provided which may be clamped by a screwthreaded clamping collar 29 screwed on the collar 25, thus securing the block 26 in substantially concentric and rigid relation to the opening 24.

That end of the resistor member 13 located adacent to the open end of the mufile may be fought through an opening 31 in one of the members 15 toward the hereinbefore-described terminal device and through an opening 32 in the end disk 16 and be suitably secured to one of the terminal members 27. The other end of the re sistor member 13 may be brought through a substantially similar opening 32 to the other of the terminal bars 27 and secured thereto in any suitable or desired manner.

Supporting members 33 are secured to each of the end caps 21 and 23 and support the assembled furnace structure on a suitable base 34. Screws 35 and nuts 36 may be employed to hold the securing members against the base 34. A work-supporting member 37 is provided adjacent the open end of the mufiie 12 and may comprise a sheet-metal member bent to substantially L-shape and with the portion provided with a small, integral flange topermit of securing one end thereof on the base 34 by screws 35 and nuts 36.

A suitable contact plug may be employed to connect the resistor, through the terminal bars 27, to a suitable source of supply of electric energy and it may be noted that the heat-insulating material interposed between the heating element proper and the terminal device is effective to permit of operating the terminal device at a relatively low temperature which does not injure the metal parts thereof, even though the temperature within the muflie is relatively high.

The device embodying my invention provides a relatively small tubular furnace which may be employed in a variety of work and for a variety of uses, such as the heat treatment of relatively small metallic objects, or it may be employed by operators for heating relatively small soldering irons or for effecting brazing operations on relatively small objects.

Various modifications in the arrangement and location of parts may be made within the spirit and scope of my invention, and such modifications are intended to be covered by the appended claims.

I claim as my invention 1. In an electric-resistance Ifurnace', in combination. a base, a tubular casing, end caps for said casing, each having a central circular opening therethrough, means forv supporting s id casing above said base secured to said end caps, aheat-insulating lining within said casing, a tubular muflle, a stop member projecting into said mutlle at one end thereof, a disc of heat-insulating material in said casing adjacent to said stop member and to one of said end caps, a terminal member operatively supported by the end cap located adjacent to said disc of heatinsulating material, and located in axial alinemcnt with said tubular mmlle. and a work-supporting member at the other end of said casing.

2. In an electric-resistance furnace, in combination. a base. a tubular casing, end caps for said casing. each having a central circular opening thercthrough, means for supporting said casing above said base sccured to said end caps, a heat-insulating lining within said casin atubular mullie within said lining. a resistor on said muflie, a stop member projecting into said mutlie at one end thereof, a disc of heat-insulating material in said casing adjacent to said stop member and to one of said end caps. a terminal -n1ember projecting outwardly through the opening in the end cap located adjacent to said disc of heat-insulating material. and means having a screw-threaded engagement with said end cap. for holding said terminal member in its proper operative position in said opening.

In testimony whereof. I have hereunto subscribed my name this 15th day of Sept,

JAMES C. WOODSON. 

